1. Field of the Invention
This invention relates to a copying apparatus, and more specifically, to a copying apparatus capable of forming an image on both surfaces of a copying paper as required.
2. Description of the Prior Art
It is often desired to form an image on both surfaces of a copying paper in order to save copying paper sheets and reduce the number of documents to be preserved, and copying apparatus capable of forming an image on both surfaces of a copying paper as required have recently been proposed and come into commercial acceptance.
A typical example of such a copying apparatus comprises a housing, a photosensitive member disposed within the housing, an image-forming means for forming an image on the photosensitive member, a copying paper conveying passage defined within the housing and extending through a transfer zone in which the image on the photosensitive member is transferred to a copying paper, a copying paper feed means for feeding a copying paper to the upstream end of the paper conveying passage, a copying paper returning passage defined with the housing, a conveyance control means disposed within the housing, and a copying paper receiving and delivering means disposed within the housing. The conveyance control means is adapted to be selectively held at a first position for discharging the copying paper conveyed through the paper conveying passage and a second position for conducting the copying paper conveyed through the paper conveying passage to the paper returning passage. The copying paper receiving and delivering means receives the copying paper returned through the paper returning passage, and delivers the received paper to the upstream end of the paper conveying passage.
In this copying apparatus, an image is formed on one surface of the copying paper while it is conveyed through the paper conveying passage after being fed from the paper feed means. When it is desired to form an image only on one surface, the copying paper having the image formed on one surface is discharged outside the housing. On the other hand, when it is desired to form an image on both surfaces of the copying paper, the copying paper having the image formed on one surface is then introduced into the paper returning passage and returned to the paper receiving and delivering means through the paper returning passage. It is delivered again to the paper conveying passage from the paper receiving and delivering means, and while being reconveyed through the paper conveying passage, an image is formed on the other surface of the paper. The paper having the image formed on both surfaces is then discharged out of the housing.
The conventional apparatus, however, has the following problems to be solved.
Firstly, in the event of paper jamming in the paper receiving and delivering means disposed within the housing, the jamming paper must be removed by performing such an operation as opening of various portions of the housing. It is not sufficiently easy and rapid therefore to remove the jamming paper and resume the copying operation.
Secondly, it is generally far less frequent to require image formation on both surfaces of a copying paper than to require it on one surface. Most of the time during which the copying apparatus is in motion, an image is formed only on one surface of a copying paper. In this one surface copying mode, the paper receiving and delivering means does not function at all. For an increased efficiency of copying, it is desired to feed copying paper sheets of various sizes selectively to the paper conveying passage. This, however, necessitates an increased number of paper feed means, and will result in an increase in the size of the copying apparatus and the cost of producing it.
Thirdly, the conveyance control means, the paper returning passage and the paper receiving and delivering means which enable an image to be formed on both surfaces of a copying paper are relatively complex in structure, and the cost of production is relatively high.